How to Successfully Tackle Moss on Your Lawn

Painstakingly laid new lawns are often overtaken with moss within just a few years. The reasons are always the same: mistakes in laying or maintaining the lawn, often both. Here’s how to make sure your lawn stays moss-free.

Apr 09, 2021 02:26 pm
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Moss on the lawn

A mossy lawn ruins even the most beautiful garden

Mosses are very ancient, adaptable plants that spread through spores, just as do. A lawn where the grass isn’t growing well, leaving gaps in what should be a lush green carpet. For lasting moss suppression, it’s therefore important that you analyze the causes behind disrupted grass growth and get to the bottom of these. If you just treat the symptoms, the moss will simply keep on coming back, meaning you have to fight it year after year.

    If you have moss on your lawn, one of the following reasons is usually the culprit:

    • A lack of nutrients (especially nitrogen)
    • Heavy, compacted soil, mostly combined with waterlogging
    • Unsuitable seed blends, such as “Berliner Tiergarten”
    • Too much shade, e.g. under tree crowns
    • Too low a pH, so soil that is too acidic (grass cannot thrive in soil under a pH of 5 (sand) or 6 (loam))
    • Mowing too short and/or not often enough

    Before you start tackling the root causes of your moss infestation, you should physically remove the moss from your lawn. A scarifier isn’t always necessary – simply using a rake to remove mossy growth from the lawn should suffice.

    Moss on a lawn: how to tackle the causes

    As the most common reason, nutrient deficiency can be treated relatively easily with the right and a little more discipline with feeding in future. A high-quality fertilizer with a high potassium content promotes resilience and stability in grass. An organic lawn feed with iron is ideal. The rapid, long-term uptake of nutrients guaranteed by this fertilizer lets the grass quickly form new green blades, filling any gaps in your lawn as its outward growth increases. As a result, the lawn uses its own strength to crowd out moss as well as . The organic nutrient components have the benefit of promoting the activity of microorganisms and therefore the decomposition of lawn thatch. In the best possible case, you can even avoid having to use a scarifier in future.

    Fertilizing a lawn
    A fertilizer with a high potassium content increases the lawn’s resilience

    Annual feeding prevents moss from spreading on the lawn in future. Above all, it’s important to fertilize in spring using an organic lawn feed and at the beginning of September in fall using a potassium-forward fall feed. Observations have shown that the slow, continuous nutrient release of organic lawn food encourages grass to grow outwards, while cheaper mineral fertilizers predominantly make grass shoot upwards.

    Moist, loamy soil

    Moss thrives in consistently wet environments. So at least the top 3.94 to 5.91 inches of soil under the grass should ideally be permeable.

    Sanding the lawn
    Moist soil can be improved by mixing in sand

    If the soil is very loamy and damp, the only remedy is regular sanding: Each spring, after the first of the year, add a layer of coarse builder’s sand 0.79 to 1.18 inches thick to the lawn and distribute using a tool such as a level rake. The layer should be thick enough so that only the tips of the grass blades poke out from the sand by around 0.39 inches. If you repeat this each spring, you should generally be able to see a visible change after three to five years: the lawn will look more full of life, and moss growth will be significantly suppressed. The addition of a soil activator has proven useful in moist, loamy ground. This consists of humus and microorganisms, and promotes soil life while also ensuring that organic residue (such as grass cuttings, which bond with the turf over time and cause matting) can better decompose. If you want to do something good for your lawn in the long term, use products with , such as “Neudorff Terra Preta” soil improver. Terra Preta contains , which contains particularly stable humus so improves soil structure in the long run.

    The right seed blend

    Grass seed always contains a blend of various grass varieties with differing properties. “Berliner Tiergarten” is a lawn blend probably recognized by all hobby gardeners. What few know is that this is not a product brand with a specific composition – quite the opposite: each producer can offer any blend of grasses under the name “Berliner Tiergarten”. Most use agricultural pasture grasses, as these are considerably cheaper than especially cultivated lawn grass varieties. These may be considerably more voracious in their growth but rarely grow outwards – this leads to gaps in the lawn, where moss and weeds can make themselves at home.

    Sowing grass seed
    When choosing grass seed, stay away from cheap blends

    If you used cheap when establishing your lawn, you should sow over the area again using a high-quality seed blend. Mow the old grass down short and scarify with the blades set low. Then, sow the new seed, spread a thin layer of turf soil all over, and thoroughly roll the whole area once. Finally, water the new lawn and keep it consistently moist for six to eight weeks.

    The problem with shady lawns

    Grass should be a last resort in heavy shade cast by trees or buildings, as it usually doesn’t form dense cover and quickly falls foul to moss. Even special shade grasses are only suitable for light shade, such as under birch or black locust.

    Lawn shaded by trees
    Lawns struggle in the shade of trees and woody shrubs

    The soil under trees is often too dry rather than too moist, so water before it’s too late and never set your lawnmower any lower than 1.97 to 2.36 inches. This will leave enough leaf surface area to absorb the scarce light. Lawns cannot permanently establish under or trees Here, dense, shade-tolerant groundcover plants such as ivy or Waldsteinia would be better choices.

    Acidified soil

    Soil with a pH (acidity level) that is too low can also promote the growth of moss. The moss itself is very pH-tolerant and will grow just as voraciously in alkaline and acidic soils. On the other hand, sandy soils with pH values under 5 and loamy soils under a pH of 6 do not offer ideal growth conditions for lawn grasses – moss has the edge on the competition here. By the way: using a moss killer such as iron(II) sulfate can lower the soil’s pH. Moreover, all lawns tend to acidify over the years as the soil is enriched with humic acid from grass cuttings and because lime washed away by precipitation is constantly being stored in deeper layers of the ground.

    An important aspect of establishing the root cause is therefore testing the pH value. Inexpensive test sets are available at garden centers. Take a little soil from a depth of around 3.94 inches at various locations, then mix these thoroughly in a container. Water the soil sample with distilled water and use the color scale to establish the pH. If it is under the stated limit, you should add to the whole surface area. You can find information on the correct dosage on the packaging.

    Prevent new moss from growing

    Correct care is the key to a moss-free lawn. Mow the area at least once a week during its whole growth period from March to November but never any shorter than 1.57 to 1.97 inches. In summer, set up a in good time if there is a dry period, as a lack of water seriously weakens grasses, allowing the lawn to really “burn” in an ongoing drought. You should also feed your lawn with an organic slow-release lawn fertilizer in spring. Depending on the product, these last three to six months, so you will generally have to fertilize your grass once more before the end of summer. If grasses are given enough nutrients, they form a carpet so dense that square goose neck moss doesn’t stand a chance.